Downhole horizontal slotting tool



March 14, 1967 J. D. WISENBAKER ETAL 3,308,893

DOWNHOLE HORIZONTAL SLOTTING TOOL 5 Sheets-Sheet Filed Dec. 51, 1963INVENTORS 5 yam/54kg@ l. ys.

United States Patent O 3,308,893 DWNHOLE HURIZUNTAL SLOTTING TOOL JohnD. Wisenbaker and Robert W. Stuart, Dallas, Tex.,

assignors of one-half each to American Coldset Corporation, Teterboro,NJ., a corporation of Texas, and

Core Laboratories, Inc., Dallas, Tex.

Filed Dec. 3l, 1963, Ser. No. 334,819 7 Claims. (Cl. 17E- 40) Thisinvention relates to a tool for making horizontal slots in the sidewallsof either cased or uncased well boreholes.

In the drilling7 and production of oil and gas wells, a horizontalslotting tool has many useful applications, principally in connectionwith well completion and well treatment.

Wells are sometimes completed by setting and cementing casing into thetop portion of the producing horiz-on and leaving the pay zone as openhole. However, in most wells the casing extends through all, or a majorportion of the productive interval, and cement lls the space between thecasing and the Wall of the borehole. The casing and the cement sheathare then perforated opposite the selected interval to permit flow offluid from the formation into the wellbore.

Common perforating techniques in commercial use today involve the use ofperforating guns which employ high explosives to re steel projectilesthrough the casing and cement sheath and into the surrounding formationor which develop high temperature, high velocity jet Streams from shapedcharges which penetrate the casing and cement sheath and a portion ofthe surrounding formation. These methods have certain disadvantages, oneof the more notable ones being that the guns frequently misfire, andsometimes the projectiles fail to penetrate the casing. Eitheroccurrence not only fails to provide the proper perforation, but alsoleaves in the well metallic debris which may seriously interfere withsubsequent operations. Moreover, the use of c-onventional perforatingguns or jets results in the formation of a limited number of relativelysmall perforations at spaced points which, particularly in denseformations of low permeability, may substantially restrict the rate ofproduction of the Well. And, further, the spent bullets and jet casesremain in the formation directly opposite the perforations andinterfere, in varying degrees, with ow into the perforations. Nopositive measure of the adequacy or inadequacy of the penetration madeby the perforating guns can be made. Thus, it is extremely difficult todetermine whether the ultimate production rate is limited by thesurrounding formation or by the inadequacy of the perforation.

Large perforations and slots are also sometimes made by means ofabrasive jet tools whereby a high velocity streams of abrasive particlesin a liquid medium is directed against the surface to be penetrated.Major disadvanytages of this procedure are that it requires the runningof pipe to conduct the abrasive uid, requires special pumping equipmentto develop required jet velocity, provides no indication of degree ofpenetration and leaves abrasive material in the hole for removal byexpensive means.

Still another way of providing perforated ycasing for the purpose ofwell completion is to pre-perforate sections of casing at the surfaceand incorporate them in the casing string at the desired point. Althoughthis method has the advantage of making it possible to provide largeropenings and even slots of any desired length, it is obviouslyrelatively expensive and troublesome. Moreover, it is extremely difcultto place the perforated section of casing at exactly the desired horizonin the well, and an error in its placement will result in opening up the3,308,893 Patented Mar. 14, 1967 Well at the wrong point, either missingthe desired formation altogether or excluding part of the desiredformation while opening up adjacent formations which may admit waterinto the well, seriously limiting or even effectively destroying itsuseful oil production capacity.

Another important use of casing perforations is in connection withsqueeze cementing operations, such as are performed in an attempt toshut off the flow of water from lower zones, close the perforations usedin drill stem testing and improve the bond or seal between the casingand the formation. These cementing operations normally involve forcing acement slurry through the casing perforations. Where the perforationsare formed by a perforating gun or jet as described above, the limitedow capacity of the relatively small, spaced perforations may restrictthe efficacy of the operation.

Casing perforati-ons are also used for such operations as hydraulicfracturing. While the fracturing uid can be injected through themultiple spaced perforations created by a perforating gun or jet,current technology favors injection of the fracturing fluid through asingle linear opening, such as the horizontal slot formed by the tool ofthe present invention, to control the plane of fracture initiation andto concentrate the fluid and achieve greater penetration of the fractureinto the surrounding formation.

Another principal use of horizontal slots is for cutting casing, forexample where the casing is to be pulled from the well. Horizontal slotsare also used for various types of well treatment, such as waterinjection, with or without tracers, and possibly for fishing and otherremedial operations.

The present invention provides a simple, inexpensive, and practicaldownhole tool for forming horizontal slots in casing or in the sidewallof uncased holes. Although the particular tool illustrated and describedherein is capable of forming only one circumferential slot at a time, itcan be used to form any number of vertically spaced slots, one after theother, during a single trip into the borehole. It will also 4beunderstood that the tool may easily he modified to provide a pluralityof vertically spaced cutting assemblies for cutting a number of slots atthe same time.

The horizontal slots formed by the tool not only afford excellentcommunication between the borehole and the surrounding formation, eitherfor purposes of well production or for purposes of injection of cementslurries, fracturing or treating liquids and the like, but also insurepositive penetration not only of the casing but of the cement behind thecasing and even the adjacent portion of the surrounding formation, ifdesired, and obviate leaving in the borehole any metallic debris orother junk which might interfere with subsequent operations.

Since the slotting tool of the present invention may be lowered into theborehole on a wire line, and does not involve one or more round tripsinto the hole with pipe, as in the case of most prior slotting tools,its operation is rapid and inexpensive. Moreover, it is possible toposition the slots at the desired depth with extreme accuracy. Forexample, the slotting tool may be lowered into the borehole on the samewire line apparatus which was employed in making the usual downholeelectrical or radioactivity logs, so that, even though there is anindeterminate error in the absolute depth indication of the wire linedepth gauge, so long as its indications are repro-ducible, the slottingtool can be positioned at a depth corresponding to any selected point onthe downhole log. Alternatively, the electrical or radioactivitydetector sonde may be lowered into the borehole simultaneously with theslotting tool, with the two in predetermined spatial relation on thesame wire line, so that the electrical or radioactivity plot may betraced or retraced until the desired point is reached.

I n addition, the downhole radioactivity log may be correlated with asurface log of radioactivity made on core samples at the surface of theground according to the method disclosed in U,S. Patent No. 3,025,398,to insure that the slotting tool is positioned to perforate the casingopposite the formation from which any selected core sample or group ofsamples was taken. Similarly, the downhole radioactivity log from thewell in question may be correlated with downhole radioactivity logs madein adjacent wells to position the slotting tool adjacent a selectedformation which is thus clearly identied from well to well.

In the drawings:

FIGURE l is a foreshortened vertical sectional view through a casedborehole containing a horizontal slotting tool embodying7 features ofthe present invention, with the tool being shown partly broken away toreveal its inner construction.

FIGURE 2 is a vertical sectional view, at enlarged scale, through thelower portion of the tool of FIGURE 1.

FIGURE 3 is a fragmentary vertical sectional view, at still furtherenlarged scale, through a lower portion of the tool, showing inparticular the scriber for recording the extent of penetration of thecutter blades.

FIGURES 4, 5 and 6 are transverse sectional views taken respectivelyalong the lines 4 4-, 5 5 and 6 6 of FIGURE 2, and at the same scale asFIGURE 2.

FIGURE 7 is an enlarged, fragmentary longitudinal sectional view takenon the line 7 7 of FIGURE 6.

FIGURES 8 and 9 are respectively staggered longitudinal and transversesectional views through the lower end portion of the tool with thecutter blades shown in the fully extended position.which they occupyduring the latter portion of the slotting operation.

In FIGURE 1, the reference numeral 10 identifies the sidewall of atypical well borehole which is lined with a steel casing 12, with cement14 filling the annular space between the casing 12 and the sidewall it).Shown suspended in the borehole on a wire line 16 as an illustrativeslotting tool embodying features of the present invention.

The tool includes a tubular housing 18 enclosing an elongated electricmotor 20 which is axially supported in the housing by spacers 22.Removably attached to the drive shaft 24 of the electric motor 2G andprojecting downwardly below the lower edge of the tubular housing 18 isa rotor assembly which is generally designated 26 in FIGURE l and isshown in greater detail in FIGURES 2-9.

As best seen in FIGURE 2, the rotor assembly is supported on an axialshaft 28 which is removably attached at its upper end to the motor shaft24 and carries at its lower end a supporting block 30 which is fixed toit by a removable pin 31. The block 3) is provided with a deepcircumferential slot 30a in which a pair of cutter blades 32 arereceived, the cutter blades 32 being keyed by pins 34 on jack shafts 36which are rotatably supported in the upper and lower portions of theblock 38. Washers 38 interposed between the upper and lower faces of thecutter blades 32 and the adjacent faces of the slot 30a in the block 30tix the shafts 35 against axial movement in the block 30 and preventengagement of the cutter blades 32 with the upper and lower faces of theslot 30a to permit easy rotation of the cutter blades 32.

Keyed to the upper ends of the jack shafts 36 by pins 40 are pinions 42which mesh with a ring gear 44 keyed to a sleeve 46 which is rotatablysupported on the shaft 28 between the upper face of the block 3i) andthe lower face of the mounting flange 28a at the upper end of the shaft28. Supported on the sleeve 46 and extending radially outward therefromis a set of four symmetrically spaced varies 48 which, like theremainder of the cutter assembly 26, are immersed in the drilling mudwhich is circulated into and out of the borehole during the rotarydrilling operation and which remains in the well to prevent blowoutsuntil the well has 'been completed for production.

As will be understood, the two cuter blades 32 always move inwardly andoutwardly in unison, being coupled together through their respectivepinions 42 and the ring gear 44 (FIGURES 2 and 4). As best 'shown inFIG- URE 6, the cutter blades 32 are normally retained in their innerposition, fully retracted within the slot Sila of the lock 3i), in whichposition they are shown in full lines in FIGURE 6, by a detent 50 whichengages the outer edge of one of the two cutter blades 32. As shown indetail in FIGURE 7, the detent 5i) is received in a recess 3ilb in thelower portion of the block 30 and is urged upwardly by a helical spring52 which is cornpressed between the lower end of the recess 30b and theunder surface of the enlarged head portion of the detent Si). The upwardmovement of the detent 50 under the iniluence of the spring 52 islimited by engagement of a head 50a formed on the lower end of thedetent 50 with the under surface of the block 30. The upper surface ofthe detent 5t) which projects upwardly into the slot 30a in the path ofone of the cutter blades 32 is beveled so that it can be cammeddownwardly against the resistance of the spring S2 by the edge of thecutter blade 32 to permit movement of the cutter blade to and from itsinner, retracted position.

As shown in FIGURES 2 and 5, mounted in the ring gear 44 and projectingdownwardly from the lower face thereof is a stop pin 54 which projectsinto an arcuate slot 30C formed in the upper surface of the block 30.Engagement of the pin 54 with the ends of the slot 30C limits themovement of the cutter blades 32.

As shown in FIGURE 2, also supported in the ring gear 44 is a styluswhich is generally designated 56 and which is shown in greater detail inFIGURE 3. As may be seen in the latter figure, the stylus 56 is slidablyreceived in a recess 44a in the ring gear 44 and is urged downwardly bya helical spring 58 which is compressed between the upper end of thestylus 56 and the inner face of a plug 6) which is threaded into theupper end of the recess 44a. The pointed lower end of the stylus 56projects into an arcuate recess 38d formed in the upper surface of theblock 3i? and bears against an arcuate sheet 62 of soft and readilymalleable material, such as lead, which tits snugly in the slot 36d andis supported on its bottom surface. As the ring gear 44 rotates,rotating the pinions 42 to swing the cutter blades 32 outwardly, thestylus 56 inscribes a readily visible mark in the malleable sheet 62,the angular extent of this mark being indic ative of the degree ofextension of the cutter blades 32.

The tool may also be provided with means for centering the housing 18 inthe borehole. The particular means illustrated in FIGURE l is of theconventional spring-basket type, including a plurality of spring fingerswhich are positioned in vertical slots 18a spaced around the housing 18.The upper ends of the ngers are xed to a cylindrical band 72 which inturn is secured to the housing 18, while their lower ends are secured toanother band 74 which is slidable vertically of the housing 18. When thelower band 74 is in its lowermost position, as shown in full lines inFIGURE 1, the spring fingers 70 `are tlat against the sides of thehousing 18; when the lower band 74 is raised, the spring fingers 7i) arebowed outwardly, as shown in broken lines, thus engaging the sidewallsof the borehole to center the housing 18 in the borehole.

The lower band 74 is actuated by cables 76 secured thereto and extendingupwardly along the inner walls of the housing 18, around pulleys 78rotatably supported on the housing and nally around a drum 80. The drum8l) is driven through a slipping clutch 82 by a fractional horsepowerelectric motor 84.

While only one centering assembly is shown, it will be understood andtwo or more centering devices of this or other type could be provided.

The operation of the tool is as follows:

The tool is lowered into the borehole on the wire line 16 to the desireddepth, as determined in the manner hereinabove described. When the toolhas reached the desired depth, the feeding of the wire line 16 isstopped and electrical power is supplied to the motor S4 through a pairof conductors in an electrical cable associated with the wire line 16(not separately shown), said current being controlled by a switch on thecontrol panel 64 at the surface of the ground. This causes the motor S4to rotate, driving the drum 80 to reel in the cables '76. This raisesthe lower band 74 and causes the spring ngers 70 to bow outwardly intoengagement with the sidewalls and center the housing 18 in the borehole.When the spring lingers 70 are in rm compressive engagement with thesidewalls and thus strongly resist further upward movement of the lowerband 74, the slipping clutch 82 will slip during continued running ofthe motor 84.

Power is then supplied to the motor 20 through a separate pair ofconductors in the electrical cable, and a separate switch on the controlpanel 64, causing motor 20 to rotate the rotor assembly 26 at arelatively high speed in the clockwise direction, as viewed in FIGURE 6.The immersionfof the vanes 48 in the drilling fluid creates a resistanceto rotation of the vanes 48 and the sleeve 46 on which they are fixedand thus causes the ring gear 44 to rotate in a counterclockwisedirection relative to the shaft 28 and block 30, as illustrated inFIGURE 4. This rotation of the ring gear 44 rotates the pinions 42 in aclockwise direction and causes the cutter blades 32 to move outwardlyfrom their normal inner positions, in which theypare shown in full linesin FIGURE 6, to outer positions in which they are shown in broken linesin that figure, the detent 50 being cammed out of the way by the edge ofone of the blades 32 during such movement.

The outer end portions of the two cutter blades 32 are studded withindustrial diamonds or other hardened, projecting cutter elements, asindicated at 32a in FIGURES 6, 8 and 9. As the rotating blades come intoengagement with the inner surface of the casing 12, they thereforecommence to cut into the casing, the centrifugal force imposed upon theblades, as Well as the rotational force imposed upon them through thegears 42 and 44 from the vanes 48, furnishing the pressure of the bladesagainst the work surface necessary to effect an eflicient and relativelyrapid cutting operation. As shown in FIGURES 8 and 9, the cutting maycontinue until there is formed a slot 66 which extends not only throughthe casing 12 but also through Ithe cement 14 behind it and for somedistance into the surrounding formation.

When the cutting operation has been completed, the electrical currentsupplied to the motor 20 from the con- 4trol panel 64 is reversed orshifted in phase, causing the motor 20 "to be driven in the oppositedirection. Thus, the rotation imparted to the vanes 48 and sleeve 46relative to the remainder of the rotor assembly is reversed with respectto that previously described and this rotates the gears 42 in theopposite direction, withdrawing the cutter blades 32 into their innerretracted positions, against the resistance of the detent 50, whichholds them in place once they have reached their fully retractedpositions, as shown in full lines in FIGURE 6. The electrical power tothe motor 84 which actuates the centering assembly is reversed or shutoff, reversing or stopping the motor 84, thereby relaxing the tension onthe cables 76 and allowing the inherent resiliency of the spring ngers70 to straighten them again, retracting .them from contact with thesidewall and against the housing 18.

The tool may then be withdrawn from the Well, and the degree ofpenetration of the slot 66 ascertained by removing the pin 31, slidingthe block 30 and its associated shafts 36 and gears 42 olf the end ofthe drive shaft 28, and examining the line inscribed on the malleablesheet 6 62. The inscribed sheet 62 is removed and replaced by a freshsheet preparatory to reusing the tool.

From the foregoing description, it will be appreciated that the presentinvention thus provides an extremely simple and practicable tool whichcan be lowered into a borehole on a single wire line and used forrapidly forming horizontal (Le. peripheral) slots in either cased oruncased wells and which will afford a positive indication of the degreeof penetration of the slots thus formed. It will .therefore beappreciated that the aforementioned and other desirable objectives havebeen achieved. However, it should be emphasized that the particularembodiment of the invention which is described herein and illustrated inthe accompanying drawings is intended as merely illustrative of theprinciples of the invention rather than as restrictive of the scopethereof, which is defined by the appended claims.

We claim:

1. A down-hole horizontal slotting tool comprising a support assemblyadapted to -be lowered on a wire line into an at least partiallyliquid-filled well borehole, centering members mounted at spacedpositions around said support assembly for movement between extendedpositions at which they engage the sidewalls ofksaid borehole to resisttransverse and rotational movements of said support assembly andretracted positions clear of said sidewalls, and means for moving saidcentering members between said extended and retracted positions, a motoron said support assembly, a rotor assembly projecting from said supportassembly and mechanically coupled to said motor to be rotated therebyabout a vertical axis, cutter elements movably mounted at angularlyspaced positions on said rotor assembly for movement in a horizontalplane toward and away from said axis, a vane assembly mounted on saidrotor assembly for limited rotational movement relative thereto, vaneson said vane assembly arranged to be immersed in the liquid in saidborehole to impart a drag against rotation of said vane assembly andurge it to rotate relative to said rotor assembly, and meansmechanically coupling said vane assembly to said cutter elements wherebysuch relative rotation of said vane assembly causes outward movement ofsaid cutter elements when said rotor assembly is rotated in onedirection and inward movement of said cutter elements when said rotorassembly is rotated in the opposite direction.

2. A down-hole horizontal slotting tool comprising a housing adapted tobe lowered on a wire line into an at least partially liquid-filled wellborehole, centering members mounted at spaced positions around saidhousing for radial movement between extended positions at which theyengage the sidewalls of said borehole to resist transverse androtational movements of said housing and retracted positions clear ofsaid sidewall, and means for moving said centering members lbetween saidextended and retracted positions, a motor in said housing, a rotorassembly projecting below the lower end of said housing and mechanicallycoupled to said motor to be rotated thereby about a vertical axis,cutter elements movably mounted at angularly spaced positions on saidrotor assembly for movement in a horizontal plane toward and away fromsaid axis, a vane assembly mounted on said rotor assembly for limitedrotational movement relative thereto, vanes on said vane assemblyarranged to be immersed in the liquid in said borehole to impart a dragagainst rotation of said vane assembly and urge it to rotate relative tosaid rotor assembly, means mechanically coupling said vane assembly tosaid cutter elements whereby such relative rotation of said vaneassembly causes outward movement of said cutter elements when said rotorassembly is rotated in one direction and inward movement of said cutterelements when said rotor assembly is rotated in the opposite direction,and detent means engaging one of the aforementioned parts movablerelative to said rotor assembly to hold said cutter elements normally ina retracted position within the projected line of said housing, saiddetent means being yieldable to permit movement of said cutters to orfrom said retracted position under the forces acting upon said cuttersduring rotation of said rotor assembly.

3. A down-hole horizontal slotting tool comprising a housing adapted tobe lowered into a well borehole on a wire line, centering membersmounted at spaced positions around said housing for radial movementbetween ex tended positions at which they engage the sidewalls of saidborehole to resist transverse and rotational movements of said housingand retracted positions clear of said sidewall, and means for movingsaid centering members between said extended and retracted positions, amotor in said housing, a rotor assembly projecting below the lower endof said housing and mechanically coupled to said motor to be rotatedthereby about a vertical axis, cutter elements mounted at angularlyspaced positions on said rotor assembly for movement in a horizontalplane toward and away from said axis, means to urge said cutter elementsoutwardly into cutting engagement with the sidewalls of said boreholeduring rotation of said rotor assembly and to retract said cutterelements inwardly for movement of said tool along said borehole, ascriber element mechanically coupled to at least one of said cutterelements for movement therewith, and a malleable element mounted on saidrotor assembly in cooperative relation to said scriber element wherebysaid scriber element will make a mark in said malleable elementindicative of the extent of outward movement of said cutter elements.

4. A down-hole horizontal slotting tool comprising a housing adapted tobe lowered on a wire line into an at least partially liquid-filled wellborehole, centering members mounted at spaced positions around saidhousing for radial movement between extended positions at which theyengage the sidewalls of said borehole to resist transverse androtational movements of said housing and retracted positions clear ofsaid sidewall, and means for moving said centering members between saidextended and retracted positions, a motor in said housing, a rotorassembly projecting below the lower end of said housing and mechanicallycoupled to said motor to be rotated thereby about a vertical axis,cutter elements movably mounted at angularly spaced positions on saidrotor assembly for movement in a horizontal plane toward and away fromsaid axis, a vane assembly mounted on said rotor assembly for limitedrotational movement relative thereto, vanes on said vane assemblyarranged to be lmmersed in the liquid in said borehole to impart a dragagainst rotation of said vane assembly and urge it to rotate relative tosaid rotor assembly, means mechanically coupling said vane assembly tosaid cutter elements whereby such relative rotation of said vaneassembly causes outward movement of said cutter elements when said rotorassembly is rotated in one direction and inward movement of said cutterelements when said rotor assembly is rotated in the opposite direction,a stylus and a replaceable soft metal member mounted in cooperativerelation, one on said rotor assembly and the other on one of theaforementioned parts movable relative thereto, whereby said stylus willscribe an arcuate line in said soft metal member having an angularlength indicative of the extent of outward movement of said cutterelements.

5. A down-hole horizontal slotting tool comprising a housing adapted tobe lowered on a wire line into an at least partially liquid-filled wellborehole, centering members mounted at spaced positions around saidhousing for movement between retracted positions adjacent said housingand extended positions in which said centering members engage thesidewall of said `borehole to urge said housing toward a centralposition in said borehole and to resist rotation ot said housing, rstand second motors in said housing, drive means mechanically connectingsaid centering members to said first motor for driving said centeringmembers outwardly to said extended position, spring means for returningsaid centering members to said retracted position upon stopping of saidrst motor, a rotor assembly projecting below the lower end of saidhousing and mechanically coupled to said second motor to be rotatedthereby about a vertical axis, cutter elements movably mounted atangularly spaced positions on said rotor assembly for movement in ahorizontal plane toward and away from said axis, a vane assembly mountedon said rotor assembly for limited rotational movement relative thereto,vanes on said vane assembly arranged to be immersed in the liquid insaid borehole to impart a drag against rotation of said vane assemblyand urge it to rotate relative to said rotor assembly, and meansmechanically coupling said vane assembly to said cutter elements wherebysuch relative rotation of said vane assembly causes outward movement ofsaid cutter elements when said rotor assembly is rotated in onedirection and inward movement of said cutter elements when said rotorassembly is rotated in the opposite direction.

6. A down-hole horizontal slotting tool comprising a housing adapted tobe lowered on a wire line into an at least partially liquid-tilled wellborehole, centering members mounted at spaced positions around saidhousing for radial movement between extended positions at which theyengage the sidewalls of said borehole to resist transverse androtational movements of said housing and retracted positions clear ofsaid sidewall, and means for moving sai-d centering members between saidextended and retracted positions, a motor in said housing, a rotorassembly projecting below the lower end of said housing and mechanicallycoupled to said motor to be rotated thereby about a vertical axis,cutter elements pivotally mounted at angularly spaced positions on saidrotor assembly for movement in a horizontal plane toward and away fromsaid axis, a vane assembly mounted on said rotor assembly for limitedrotational movement relative thereto, vanes on said vane assemblyarranged to be immersed in the uid in said borehole to impart a dragagainst rotation of said vane assembly and urge it to rotate relative`to said rotor assembly, means mechanically coupling said vane assemblyto said cutter elements whereby such relative rotation of said vaneassembly causes outward movement of said cutter elements when said rotorassembly is rotated in one direction and inward movement of said cutterelements when said rotor assembly is rotated in the opposite direction,a stylus and a soft metal sheet mounted in cooperative relation one onsaid rotor assembly and the other on one of the aforementioned partsmovable relative thereto, whereby said stylus will scribe an arcuateline in said soft metal sheet having an angular length indicative of theextent of outward of said cutter elements, and a detent effectivelyengaging said cut-ter elements and normally holding them in a retractedposition within the projected line of said housing, said detent beingyieldable to permit movement of said cutters to or from said retractedposition under the forces acting upon them during rotation of said rotorassembly.

7. A down-hole horizontal slotting tool comprising a housing adapted tobe lowered on a wire line into an at least partially liquid-filled wellborehole, centering members mounted at spaced positions around saidhousing for movement between retracted positions adjacent said housingand extended positions in which said centering members engage thesidewall of said borehole to urge said housing toward a central positionin said borehole and to resist rotation of said housing, iirst andsecond motors in sai-d housing, drive means mechanically linking saidrst motor and said centering members whereby said motor drives saidcentering members between said retracted and extended positions, saiddrive means including a slipping clutch which slips when said centeringmembers are in firm engagement with said sidewall, a rotor assemblyprojecting below the lower end of said housing and mechanically coupledto said second motor to be rotated thereby about a vertical axis, cutterelements pivotally mounted at angularly spaced positions on said rotorassembly for movement in a horizontal plane toward and away from saidaxis, a vane assembly mounted on said `rotor assembly for limitedrotational movement relative thereto, vanes on said vane assemblyarranged to be immersed in the uid in said borehole to impart a dragagainst rotation of said vane assembly and urge it to rotate vrelativeto said rotor assembly, means mechanically coupling sai-d vane assemblyto said cutter elements whereby such relative rotation of said vaneassembly causes outward movement of said cutter elements when said rotorassembly is rotated in one direction and inward movement of said cutterelements when said rotor assembly is rotated in the opposite direction,a stylus and a soft metal sheet mounted in cooperative rela-tion one onsaid rotor assembly and the other on one of the aforementioned partsmovable relative thereto, whereby said 20 stylus will scri-be an arcuateline in said soft metal sheet having an angular length indicative of theextent of outward movement of said cutter elements, and a detenteffectively engaging said cutter elements and normally holding them in aretracted position within the projected line of said housing, saiddetent being yieldable to permit movement of said cutters to or fromsaid retracted position under the forces acting upon them duringrotation of said rotor assembly.

References Cited by the Examiner UNITED STATES PATENTS Re. 19,281 8/1934Schroeder 175--292 X 1,358,818 11/1920 Bering l66-55.7 2,280,769 4/1942Page 166--55.7 X 2,621,898 12/1952 Brodhead 175-292 X 2,879,038 3/1959Johnson 175-292 X CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

N. C. BYERS, Assistant Examiner.

1. A DOWN-HOLE HORIZONTAL SLOTTING TOOL COMPRISING A SUPPORT ASSEMBLYADAPTED TO BE LOWERED ON A WIRE LINE INTO AN AT LEAST PARTIALLYLIQUID-FILLED WELL BOREHOLE, CENTERING MEMBERS MOUNTED AT SPACEDPOSITIONS AROUND SAID SUPPORT ASSEMBLY FOR MOVEMENT BETWEEN EXTENDEDPOSITIONS AT WHICH THEY ENGAGE THE SIDEWALLS OF SAID BOREHOLE TO RESISTTRANSVERSE AND ROTATIONAL MOVEMENTS OF SAID SUPPORT ASSEMBLY ANDRETRACTED POSITIONS CLEAR OF SAID SIDEWALLS, AND MEANS FOR MOVING SAIDCENTERING MEMBERS BETWEEN SAID EXTENDED AND RETRACTED POSITIONS, A MOTORON SAID SUPPORT ASSEMBLY, A ROTOR ASSEMBLY PROJECTING FROM SAID SUPPORTASSEMBLY AND MECHANICALLY COUPLED TO SAID MOTOR TO BE ROTATED THEREBYABOUT A VERTICAL AXIS, CUTTER ELEMENTS MOVABLY MOUNTED AT ANGULARLYSPACED POSITIONS ON SAID ROTOR ASSEMBLY FOR MOVEMENT IN A HORIZONTALPLANE TOWARD AND AWAY FROM SAID AXIS, A VANE ASSEMBLY MOUNTED ON SAIDROTOR ASSEMBLY FOR LIMITED ROTATIONAL MOVEMENT RELATIVE THERETO, VANESON SAID VANE ASSEMBLY ARRANGED TO BE IMMERSED IN THE LIQUID IN SAIDBOREHOLE TO IMPART A DRAG AGAINST ROTATION OF SAID VANE ASSEMBLY ANDURGE IT TO ROTATE RELATIVE TO SAID ROTOR ASSEMBLY, AND MEANSMECHANICALLY COUPLING SAID VANE ASSEMBLY TO SAID CUTTER ELEMENTS WHEREBYSUCH RELATIVE ROTATION OF SAID VANE ASSEMBLY CAUSES OUTWARD MOVEMENT OFSAID CUTTER ELEMENTS WHEN SAID ROTOR ASSEMBLY IS ROTATED IN ONEDIRECTION AND INWARD MOVEMENT OF SAID CUTTER ELEMENTS WHEN SAID ROTORASSEMBLY IS ROTATED IN THE OPPOSITE DIRECTION.